The invention relates to the use of shatterproof laminated window assemblies having high reflection of solar radiation in combination with a unique visual appearance not previously found for use in architectural and automotive applications.
The surface areas of automotive glass have increased in recent years because of the popularity of new Sport Utility Vehicles (SUV's) in the United States and elsewhere which has resulted in the need to reduce vehicle solar heat load. In addition, there has been a strong interest for increased vehicle privacy to improve personal security. Because the rear and back glass as well as sunroofs for such vehicles are usually controlled by less restrictive government regulatory rules on visible light transmittance, high performance heat reflecting and/or heat absorbing glass with accompanying low visible light transmittance and with limited aesthetic options has grown in use.
In architectural building applications metal-coated glass with high visible reflectance is not desirable because of the objectionable “mirror-like” reflections. Furthermore, in some high building density city regions such glass is not allowed by building codes because of the impact of reflected light onto nearby structures.
The present invention relates to encapsulated solar reflecting films for use in laminated window assemblies and more particularly to shatterproof window assemblies having a safety glass type of construction. Solar reflecting window assemblies have found application in numerous applications where one objective is to manage internal heat loads by reflecting the near infrared portion of the solar spectrum which causes heating. This type of technology has been employed, for example, in commercial and residential glazing products as well as automotive window products.
To reduce the heating effects resulting from such windows, selective light transmitting materials or films have been incorporated into window assemblies. These films have generally been designed to maximize rejection of incoming light in the near infrared wavelength range, maximize visible light transmittance and minimize visible light reflectance. Selective light transmitting films are disclosed, for example, in U.S. Pat. No. 4,973,511.
Angstrom-thick (or thicker) layers of metals, metal compounds, and the like in windows to reflect heat-producing infrared solar radiation while transmitting significant cooler visible light are well known. Temperature increase is reduced within an area delimited by one or more of such windows. These layers usually arranged in sequence as stacks, and are carried by an appropriate transparent planar polymeric support layer, such as biaxially stretched, thermoplastic polyethylene terephthalate film (PET) or equivalent material. As used hereinafter, the polymeric support layer having the metal coating will collectively be referred to as a “metallized film.”
When a metallized film is combined with glass in a laminated safety glazing, two layers of a shock-dissipating interlayer of plasticized polyvinyl butyral (PVB) are usually included to absorb a blow from a foreign object without penetrating the glass. As disclosed in U.S. Pat. No. 5,091,258, the contents of which are herein incorporated by reference, a metal coating is disposed onto a flexible plastic substrate such as PET (forming a metallized film) and is encapsulated within two layers of plasticized PVB. This multi-layered laminate with PVB as the outer layers is then laminated between two rigid transparent members such as glass to form the safety glazing which, by virtue of the presence of the metallized film, reduces solar radiation transmission.
Any nonplanar distortions of the metallized film in the laminate structure have been recognized in the prior art as being problematic, and, when pronounced, have been labeled as ‘defects’ that render the glass laminate commercially unacceptable. These ‘defects’ are visually apparent because there is almost always a small amount of visible light being reflected from the surface of the metallized film. The '511 patent sought to reduce this ‘defect’ by designing the metallized film to minimize visible reflectance at the PVB/metallized film interface so as to significantly reduce an observer's ability to see the optical ‘defects’ present in the glass laminate.
Another attempt to deal with this optical ‘defect’ is described in U.S. Pat. No. 4,465,736, which also sought to minimize surface deformities in the metallized film. The '736 patent discloses a solar reflecting metal/dielectric stack, therein called a coating, disposed onto a special substrate designed to be heat shrinkable within certain carefully pre-chosen limits. Furthermore, U.S. Pat. No. 5,932,329 discloses a laminated glass pane containing an IR-reflecting surface coating. The '329 patent noted that such laminated glass panes frequently exhibited a disturbing optical quality defect or optical distortion, wherein the IR-reflecting surface does not appear uniform in reflection, but exhibits a shrinkage effect or even a hammering or wrinkling effect. The '329 patent set out to remedy this problem by completely or nearly completely avoiding optical distortion by minimizing the shrinkage of the IR-reflecting surface, so as to prevent deformities or the IR-reflecting surface.
Virtually no prior art process is capable of reducing every surface deformity in the IR-reflecting surface. Because a flat mirror-like surface is very difficult to obtain, it would be desirable to develop a glass laminate structure that could advantageously use surface deformities of the IR-reflecting surface.